1. Technical Field
The present disclosure relates in general to communication devices and in particular to object detection and antenna tuning in communication devices.
2. Description of the Related Art
In many wireless communication devices, traditional approaches to object detection are implemented. For example, Transmit Power Reduction is a commonly applied technique that is used to mitigate Near Field Electromagnetic Energy Exposure when an object comes into close proximity to a transmit antenna in the wireless communication device. The level of Transmit Power Reduction is based upon determining whether object contact or proximity occurs close to the antenna elements of the wireless communication device. One of the approaches for object detection is to employ a “separate” capacitive proximity sensor “near” the antenna element to detect presence of a body/object and then to reduce transmit power.
One of the mechanisms by which the antenna performance degrades is the detuning of a narrow bandwidth antenna when the antenna of a cell-phone is touched by a person's hand. In one implementation, the capacitive proximity sensor is required to detect the presence of human body presence within a range of up to 8 to 10 mm from the sensor. This specific range is required to enable the device to meet near field electromagnetic energy exposure requirements. The physical area required to implement this particular sensor is about 500 mm squared. Even within larger sized wireless communications and/or processing devices, it is becoming difficult to find space for a separate capacitive proximity sensor for multiple antennas (e.g., the various antennas employed for 2G/3G/4G). In fact, one of the reasons antennas in a wireless communication have narrow bandwidth is due to lack of sufficient volume (area) for the antenna element. One approach to the spatial/real-estate challenge is a non-optimal SAR control solution based on orientation. This approach is commonly applied in larger devices like “tablets”. Nevertheless, the difficult challenge of finding room in wireless communications device for a separate capacitive proximity sensor to detect the presence of an object persists.